Cleaning electrical coils



Patented Mar. 1, 1949 CLEANING ELECTRICAL COILS Frank W. MacClean,Hobart, and Victor Urban, Crown Point, 1nd.

No Drawing. Application May 17, 1945, Serial No. 594.378

3 Claims. 1

This invention relates to improvements in the art of reconditioningelectrical apparatus and more particularly to electrical apparatuscomprising coils of insulated Wires.

Heretofore, electrical apparatus such as motors, coils, transformers,generators, and the like, have been cleaned with compressed air. In suchcleaning, care must be exercised that pressures used are not too great,as binding tapes or other insulation may be loosened and dirt blownthereunder.

Another method commonly employed involves dipping the apparatus in asolvent such as carbon tetrachloride, benzine or gasoline. Such cleaningnecessitates careful drying before the apparatus can be reused, and itis also objectionable in that a thin film of residual matter is left onthe cleaned surfaces which prevents good adherence of subsequentlyapplied insulating mediums as paint or varnish. This, together with thedeleterious effect on the insulating coatings, frequently results ingrounding of the electrical equipment thereby rendering it inoperative.Moreover, such methods involved either hazardous fire or workingconditions since the materials used were either quite inflammable orgave oif toxic vapors.

It is accordingly among the objects of the present invention to providea method of reconditioning electrical apparatus which overcomes theforegoing diiliculties of the prior art methods.

It is a further object to provide a method of reconditioning electricalapparatus which is very efficient and at the same time inexpensive touse.

It is another object of the present invention to provide a method ofreconditioning electrical apparatus which permits insulating material tobe quickly and readily applied after cleaning.

We have found that the inclusion of solid comminuted vegetable materialsuch as corn meal,

bran, hominy grits and the like, in an air stream.

directed under pressure, quickly cleans electrical coilsand the likewithout any harmful effects on the insulation, and at the same timeleaves the surfaces in condition for varnish or other insulatingmaterials to be immediately applied thereto.

As an example of the use of our invention, we have applied the followingprocedure'to cleaning a 1250 horsepower, 600 volt, direct current motor.After the removal of guards and cover plates, the armature winding wasgiven a resistance check and the reading secured was 200,000 ohms,whereas 600,000 ohms is generally accepted as being the safe minimumrequirement of this, type and size of motor. Compressed air was thenapplied 2 to the armature after which a second insulation test showed areading of 400,000 ohms. Following this, corn meal was introduced intothe air stream and the combined air and corn meal was thoroughly blownthrough all of the openings in the armature windings and commutatorassembly. By regulating the air pressure within the range of between 15to 30 pounds per square inch, clean surfaces can be obtained withoutharmfully aftherefrom. As a result of using the foregoing cleaningmethod, the various coils and bands of the armature present a shiningand lustrous surface appearance. A final insulation test was then madeand the reading was found to have increased to 90,000,000 ohms from theoriginal reading of 200,000 ohms. In addition, all the exposed surfaceswere absolutely dry so that it would have been possible to reassemblethe motor and place the same in operation at once, if so desired.However, a protective coating of acid'resistant insulating paint orvarnish was then applied, and it was noted that the equipment treated bythe foregoing method retained the protective coatings much better thanequipment cleaned by prior art methods, even though the latter wasthoroughly dried before such coatings were applied.

While we have described one specific embodiment of our invention, itwill be understood that this embodiment is merely for the purpose ofillustration and description and that various other forms may be devisedwithin the scope of our invention, as defined in the appended claims.

We claim:

1. The method of dry cleaning electrical coils in motors, generators,and the like, characterized by blowing on the parts to be cleaned astream of air having mixed therein solid comminuted vegetable materialof the class comprising corn meal, bran and hominy grits.

2. The method of dry cleaning electrical coils in motors, generators,and the like, characterized by blowing on the. parts to be cleaned astream of air having mixed therein solid comminuted vegetable materialthe class comprising corn 4 meal, bran and homing grits, the pressure 0!REFERENCES mm said stream being between 15 and 30 lbs. per The followingreferences are oi record in the square inch. file of this patent:

8. The method .01. reconditioning electrical 5 UNITED coils in motors,generators and the like, compris STATES PATENTS ing blowing a stream ofcompressed air thereon, Number Name Date adding corn meal to said streamand continuing 0 ,6 1 unkel May 24, 1898 the blowing of the stream onthe coils for a, suf- 3 mn July 31, 1923 iicient period of time toremove oil from the coils, 10 34.494 Gillespie Nov. 7, 1933 stopping theaddition of corn meal to the stream 1. .6 5 Williams Jan. 1, 1935 andcontinuing blowing the stream 01 air on the 2384358 i Oct. 11, 1945coils until the corn meal is rgemioved therefrom; FOREIGN PATENTS thepressure of said stream ng regulated to between and lbs. per squareinch. Y 15 gag g Fr cmmtry Date FRANK w MACCLEAR m Feb. 20, 1931 VICTORURBAN.

